MX2010013211A

MX2010013211A - Compound material based on rice husk and binder, modified with carbon nanostructures.

Info

Publication number: MX2010013211A
Application number: MX2010013211A
Authority: MX
Inventors: Jose Antonio Soto Montoya; Daniel Ramirez Gonzalez; Mauricio Martinez Alanis
Original assignee: Urbanizaciones Inmobiliarias Del Ct S A De C V
Priority date: 2010-12-01
Filing date: 2010-12-01
Publication date: 2012-06-08
Also published as: WO2012074350A1; JP2014501862A; JP6126011B2; BR112013013618A2; US9527770B2; EP2647608A4; CA2819578A1; CN103429550A; EP2647608A1; US20150005415A1; EP2647608B1

Abstract

Compound material based on water, cement, rice husk and polymeric resin modified with carbon nanostructures, in which variation of the ratios in which said components are combined together with production pressure and temperature results in a consistency suitable for said material to be used as paint, coating paste or panel-production conglomerate.

Description

COMPOSITE MATERIAL BASED ON RICE AND RUBBER CONCRETE MODIFIED WITH NANOSTRUCTURES OF CARBON.

Field of the invention.

The present invention relates to materials made with rice husk and binder, and more particularly to a material composed of rice husk with binders modified with carbon nanostructures.

BACKGROUND OF THE INVENTION Rice is a food that is consumed throughout the globe and within its processing, it is necessary to remove the shell. In particular, for each ton of rice harvested, a quarter of a ton of rice husks is generated, which is mostly treated as agricultural waste.

In Mexico alone, 337,250 tons of rice are produced per year, representing 84,312 tons of annual rice husk.

Due to the high production of rice worldwide, it is important to find applications of waste (husk), produced during processing. Its high content of silica, its geometry of uniform thickness and aspect ratio, make it a material that is economically viable to function as a filler (filler material) in agglomerates with resins, similar to the wood particles used in the manufacture of conglomerates.

Within the manufacturing process of wood agglomerates, the proportion of resin used dictates the mechanical strength of the final product. That is, the higher the resin concentration, the greater the mechanical strength, but obviously the higher production cost. From the point of view of nanostructures, carbon nanotubes, in addition to other properties, are highly resistant and can significantly increase the mechanical properties of a material, if it is used as a reinforcement nanofiller.

On the other hand, it is also known that the housing market is an important economic engine in any country and Mexico is no exception. The composition of a building intended for housing is very complex, it requires a large number of materials and labor of very varied specialties, regardless of the construction process chosen for it. However, all these constructions have similar characteristics in terms of their form and behavior. All of them are composed of walls, and a horizontal one defined by floor and roof systems.

We have seen that wood and its conglomerates can be used within a complete construction system, from structure to finishes. However, the ecological part and the cost of the different processes to treat it can be very high, and have a negative impact on the generation of affordable housing, even when generating panels manufactured with process residues and particles bound with synthetic resins. .

Within this problem, arises the idea of making materials with a better performance and more economical by combining four elements (agroindustrial waste materials, polymer resins, cement and carbon nanostructures). On the one hand, it has been shown that it is possible to mix resins with carbon nanotubes to achieve a better mechanical and driving performance. In addition, rice husk (with or without heat treatment) can become an economical material since it is a waste, and therefore it can be used to make more economical composite materials (conglomerates, pastes and paints) using a modified resin with carbon nanotubes and a cementitious material (white cement and gray portland cement). These new compounds are conceived as building materials, which can be part of the construction system due to their mechanical properties or as finishing materials allowing the construction of low-cost housing.

The material of the present invention has advanced engineering in nanotechnology, in addition to having as a base element a residue of the agricultural industry that is produced in all regions of the world and its use as forage is not possible, for which reason it is considered that it has contributions. important ecological The silicon oxide present in the scale and which is part of the composite material for the construction, does not represent a health risk since the silica is confined to the structure of the rice husk and this in turn in the polymer matrix of the material , eliminating the risk of detachment of said particles that may cause any damage to people in contact with it.

By offering fireproof properties, the material of the present invention is considered as an appropriate finish for places of mass concentration of people as a flame retardant, and this integrates an added value to the homes where it is applied.

As its constituents give it the property of not transmitting the heat that surrounds it in its face exposed to the elements (because it has a porous structure in micro scale and high content of silica) it also participates in a passive way in the saving of electrical energy to achieve comfort inside the property to which it is applied, we have found that the performance of a 3mm thick paste is significantly superior to the corresponding one of a 2 inch thick polystyrene plate.

Likewise, the composite material of the invention is constituted with ecological materials and has the faculty of being a substitute material of wood for the construction of housing, its contribution in favor of the environment reaches a high impact since it stops using materials that for its production is obtained indirectly high volumes of CO2.

In the present invention, in addition, we propose the method of mixing and pressing a cementitious material with rice husk with or without heat treatment, bonded with polymer resin modified with carbon nanostructures as reinforcing filler. The procedure allows that when varying the proportions between these materials it is possible to produce a conglomerate, a paste or a paint, with the purpose of incorporating it as a substitute and novel material in the existing constructive systems.

In summary, the rice husk material of the present invention can be used in the preparation of: Paint, with fireproof properties, great mechanical resistance and with thermal and waterproofing properties; Paste, to be applied directly on walls as a textured finish, with properties of thermal insulation in thicknesses of 2 mm or more, fireproof properties and with mechanical resistance to tension and waterproof; Y Panel, in different thicknesses and densities, with high mechanical properties in flexion, tension and compression, fireproofing and thermal insulation, as well as being resistant to constant hydrostatic pressures (without increasing thickness) for a long time and its silica content also resistant to termites, also has thermoforming properties.

Brief description of the figures.

To give a better understanding of the invention, a description thereof is given below, together with the accompanying drawings, in which: Figure 1 shows a diagram of the process for the synthesis of carbon nanostructures, using chemical vapor deposition assisted by spray (AACVD); Figure 2 shows a scanning electron microscopy image of carbon nanotubes used in the present invention; Figure 3 illustrates an image of high resolution transmission electron microscopy (with a graph scale of 500nm), which reveals the internal structure of carbon nanotubes used in the present invention; Figure 4 illustrates a high resolution transmission electron microscopy image, which reveals the internal structure and crystallinity of carbon nanotubes at higher resolution (with a 5nm graph scale) than the image of Figure 3; Figure 5 shows the X-ray pattern of the nanotubes used in the present invention; Figure 6 shows a graph of the evolution of mass with respect to temperature in thermogravimetric analysis of the nanostructures used in the present invention; Figure 7 shows the typical diffractogram of white cement; Figure 8 shows a micrograph of rice husk with a 3 mm graphic scale; Figure 9 shows a rice husk micrograph with a graph scale of 500 μm; Figure 10 shows a scale micrograph of with a graphical scale of 200 μm; Figure 1 1 shows a rice husk micrograph with a graphical 50-minute scale; Figure 12 shows a micrograph of the internal structure of rice husk with a graphical scale of 200 μm; Figure 13 shows a micrograph of the internal structure of rice husk with a graphical scale of 50 μ? T ?; Figure 14 is an image showing a spectrum with the signals associated with the chemical elements present on the surface of the rice husk; Figure 15 is an image showing a region of analysis of the surface in the rice husk; Figures 16, 17 and 18 are part of a mapping of more abundant chemical elements in the rice husk; Figure 19 is a conceptual diagram showing the components of the composite material of the present invention; Figure 20 is a schematic of the simultaneous ultrasonic scattering process; Figure 21 is a schematic of the result of the ultrasonic dispersion to the carbon structures in the medium; Figure 22 is an image showing the carbon nanotubes after the ultrasonic dispersion with a graphical scale of 2 μ? T ?; Figure 23 is an image of the virgin binder; Figure 24 is an image of the binder reinforced with carbon nanotubes; Figure 25 shows an image of the composite including scale, cement, resin and a homogeneous dispersion of the carbon nanostructures; Y Figure 26 is a comparative graph of temperature measured within devices coated with 2-inch-thick polystyrene, against another coated with 3-mm-thick paste and with the weather temperature as a reference.

Detailed description of the invention.

The charges used to modify the binder are carbon nanostructures known as multiple-walled carbon nanotubes, which are quasi-cylindrical structures composed of several concentric layers of graphite networks (hexagonal network of carbon atoms bonded together covalently). . It must be emphasized that the carbon-carbon bond is one of the most resistant in nature. However, some of the carbon atoms of hexagonal networks can be replaced by other elements or functional groups that make these tubes more reactive with molecules, polymers and external agents, and that their interactions with different matrices are greater. Within the groups or elements that can replace the carbon atoms, we can mention the N, P, O, S, Si, B, Se, etc, or functionalization with groups of the -OH, -OOH or OH type.

The dimensions of the multilayer carbon nanotubes used in this work have average lengths of 800 μm and diameters of 30-70 nm, and were synthesized with the AACVD (Aerosol Assisted Chemical Vapor Deposition) method, which employs a solution which contains the carbon source (eg hydrocarbon) and a metallic catalyst that is used to promote the growth of tubular nanostructures (eg transition metals such as Ni, Fe and Co). This solution is ultrasonically agitated in order to generate microdroplets of this mixture (Fig. 1), and through a flow of inert gas are transported through a quartz tube to the high temperature reactors where decomposition and growth occurs. Subsequent nanotubes.

Other important characteristics of the nanotubes produced in the present invention are: Reactivity, caused by the controlled presence of atoms other than carbon (doping) or by functional groups, which allows a better interaction between the carbon nanotube and the matrix in question to manufacture the compound with nanotubes; High degree of crystallinity of the nanotubes; High purity of the nanotubes (absence of non-tubular particles and amorphous carbons).

In figures 2 and 3, which correspond to scanning electron microscopy images, the purity of the nanostructures and their morphology can be observed. In figure 4, which corresponds to high resolution transmission electron microscopy image, the internal structure and crystallinity, as well as the diameters are revealed. In Figure 5, the crystallinity of the nanotubes can be confirmed. In figure 6, the absence of amorphous material is confirmed, as well as the purity, since the evolution of the mass with respect to temperature in thermogravimetric analysis in air is shown.

Another element of loading in the synthesis of the composite material based on rice husk, is the use of white cement, this being a variant of portland cement, but with a lower percentage of Fe2Ü3. Its characteristics in terms of mechanical strength are referred to, they resemble gray cement, but with a setting time is less, that is, it is more reactive, and therefore, requires a higher percentage of humidity. Figure 7 shows the typical diffractogram of white cement.

The role of white cement is to interact with the modified binder, as an additional bonding element in the material, thus providing better performance in environments of extreme humidity, as well as greater integration in concrete-like surfaces and accelerate the drying of the material.

The invention takes advantage of the mechanical properties of doped and functionalized carbon nanotubes, in order to significantly increase the mechanical properties of a compound that is used in the manufacture of conglomerates, paints, pastes or rice husk panels in the area of the building.

The key point of the present invention revolves around the interaction of the active sites on the surface of carbon nanotubes (doping), and taking advantage of the aspect ratio (length / diameter) of these nanotubes (between 30,000 and 50,000).

The basic component for the production of the composite material is rice husk, which is a byproduct of agro-industrial activities, and which can not be used as fodder, as well as being a substitute for cellulose-based materials and other natural fibers.

For morphological and chemical characterization or analysis of the materials used in this invention, scanning electron microscopy and elemental analysis studies were carried out using X-ray energy dispersion, as shown in Figures 8-18. In the micrographs of Figures 8-1 1, the surface of whole husks is observed in a general way, presenting a regular pattern of periodic "pyramidal" arrangements, the average size is 40 pm2 of base and with a regular separation between them of approximately 80 ? t ?, which will favor binding points with the modified resin.

Figures 12 and 1 3 show the internal structure, consisting of channels parallel to the entire length of the body. The diameter of the channel is close to 10 μ ??.

The following table shows the elementary quantification, presented in percentage by weight and atomic percentage, this reveals that more than 50% of rice husk is composed by S1O2.

Element Wt% At% C K 28.49 39.53 O K 40.21 41 .89 Yes K 31 .31 1 8.58 Figure 14 shows the spectrum with the signals of the elements that are on the surface of the rice husk.

In Figures 1-5, the elementary mapping analysis of a random region on the surface of the rice husk is presented. In Figure 15 the analysis region is shown, while for each of the images of Figures 16 to 18 it is generated from the point energy detection matrix for Si, O and C.

The combination of the properties of each one of the blocks gives rise to the obtaining of a composite material with special characteristics translated into better mechanical and driving performance than conventional materials.

In figure 19 the concept is represented on the nanostructured composite material of the present invention, whose properties offer a better performance than similar materials based on natural fibers and a low environmental impact compared with the elaboration of similar materials based on synthetic fibers. . Said composite material is constituted by cement, water, carbon nanostructures doped with N, P, O, S, Si, B, Se, Fe, Co, Ni, Ag, Au, Pd, Pt, etc., or functionalization with groups of the type -OH, -OOH or OH, treated thermally or with acids to cause defects in their graphitic network, rice husk and the binder or polymeric resin.

The process of making the material of the present invention begins with the mechanical grinding of the rice husk to achieve a size between 100 nm to 2 mm.

On the other hand, the process for the modification of the binder was as follows: Dispersion of the carbon nanostructures by means of an ultrasonic dispersion process, such as a tip or a bath (see Fig. 20). Figure 21 shows on the left side the binder and the carbon nanotubes before dispersion and on the right side the dispersion result is shown. The dispersion can also be seen in the image of figure 22.

Subsequently, the nanostructures were incorporated (previously dispersed) in the binder matrix at a controlled temperature, using an electro-mechanical mixer to obtain a better distribution of the nanometric loads in the matrix. Percent loads of carbon nanostructures were used from 0.001% to 10% by weight, with respect to the binder.

The binder matrix is of the polymeric type, for example polyvinyl acetate or the like. In figures 23 and 24 you can notice the difference between a virgin resin and a resin modified with carbon nanostructures (see arrows indicating the dispersion of carbon nanotubes), respectively.

Figure 25 shows the X-ray energy dispersion spectrum where it is determined that the main constituents of the composite material are the following: Element Wt% At% C K 64.3 71.89 O K 30.55 25.65 Yes K 5.15 2.46 In figure 26 it can be noted that the material of the present invention has a better performance when compared to a 2-inch polystyrene plate, the graph shows that there is at least 4 degrees centigrade difference between the internal temperature of the device measurement exposed to the weather covered with 3mm of paste of the material of this invention, and another covered with polystyrene of 2 inches of thickness, both well below the temperature of the weather just next to the devices used.

The fundamental purpose of the incorporation of carbon nanostructures is to increase the performance of the resin or binder, through which they will transfer their mechanical, electrical and thermal properties during the polymerization, resulting in a reinforcement network in the binder polymer with best properties.

In general, the procedure for the preparation of the material of the present invention is as follows: 1 . Mix processed rice husk with modified resin; 2. Dosing the load of white cement; Y 3. Homogenize the previous mixture with electromechanical means.

The variations in percentages of the materials to achieve the different presentations of the compound, are as follows (the percentages are referred to the mass of the processed husk [m]): Conglomerate: processed husk (m); white cement (20% to 80% m); modified resin with nanostructure loading (1% to 150% m); water (0% to 10% m); pressure 1 to 40 kg / cm2; temperature 18 to 150 ° C.

For the case of the elaboration of the pasta the proportions are: processed husk (m); white cement (20% to 80% m); modified resin with nanostructure loading (100% to 300% m); water (10% to 50% m); pressure 0 kg / cm2; temperature 18 to 25 ° C.

For the case of the preparation of the paint the proportions are: processed husk (m) white cement (20% to 80% m); modified resin with nanostructure loading (> 200% m); water (50% to 150% m); pressure 0 kg / cm2; temperature 18 to 25 ° C.

The fundamental difference between the three presentations is the relative amount of each of its components, water, resin modified with carbon nanostructures, rice husk, white cement, pressure and temperature, since the manufacturing process is similar for all.

The composite material in its different presentations was subjected to hydrostatic pressure tests for a period of time exceeding 40 hours, without registering permeability.

The composite material in its different presentations was subjected to direct flame combustion tests, showing fireproof properties, properties that do not exhibit conventional wood products (plywood, boards, commercial agglomerates, etc.).

The paste-like composite material was used to cover a cube of transparent material, and was placed outdoors together with a similar one covered with 2-inch polystyrene plates for more than 100 continuous hours, recording the interior temperature of the devices and comparing it with the recorded of the weather, it observes a thermal insulation capacity significantly superior to that of 2-inch polystyrene when the paste is painted white (see figure 26).

The conglomerate-type composite material was subjected to a mechanical 3-point bending test, determining the percentage increase in the performance of the specimens of material of the invention with respect to those of reference, and it was concluded that the use of carbon nanostructures as reinforcement in the resin, as well as the use of white cement, results in a 54% increase in mechanical resistance to bending.

The present invention has been described in its preferred embodiment, however, it will be apparent to those skilled in the art, that a multiplicity of changes and modifications of this invention can be made, without departing from the scope of the following claims.

Claims

Claims 1. A composite material comprising rice husk, binder modified with carbon nanostructures, water, and cement. 2. The material according to claim 1, wherein the binder is a polymeric resin. 3. The material according to claim 2, wherein the polymeric resin is polyvinyl acetate. 4. A compressed conglomerate comprising of rice husk, binder modified with carbon nanostructures, water, and cement. 5. The conglomerate according to claim 4, wherein the binder is a polymeric resin. 6. The conglomerate according to claim 5, wherein the polymeric resin is polyvinyl acetate. 7. A paint for surfaces comprising rice husk, binder modified with carbon nanostructures, water, and cement. 8. The surface paint according to claim 7, wherein the binder is a polymeric resin. 9. The surface paint according to claim 8, wherein the polymeric resin is polyvinyl acetate. 10. A paste for coating surfaces comprising of rice husk, binder modified with carbon nanostructures, water, and cement. eleven . The paste for coating surfaces according to claim 10, wherein the binder is a polymeric resin. 12. The paste for coating surfaces according to claim 1, wherein the polymeric resin is a polyvinyl acetate.